Hematopoietic stem cells (HSCs) are primitive cells capable of regenerating all blood products throughout the life of an individual, balancing their self-renewal with progeny differentiation. These fundamental characteristics are in part intrinsic and in part conferred by the microenvironment or niche in which HSCs reside. Recent studies in genetically altered animals have established osteoblastic cells as important members of the HSC niche.
Hematopoietic stem cells have therapeutic potential as a result of their capacity to restore blood and immune cells in transplant recipients. Furthermore, HSCs have the potential to generate cells for other tissues such as brain, muscle and liver. Human autologous and allogeneic bone marrow transplantation methods are currently used as therapies for diseases such as leukemia, lymphoma, and other life-threatening diseases. For these procedures, a large amount of donor bone marrow must be isolated to ensure that there are enough HSCs for engraftment.